I'd like to see a CAD of what you have in mind.
I am currently using a BP Series 1 with Centroid controls. I am soon to get rid of it for the simple fact that it's X axis is limited to 15.xx" - when I first got the mill it was great and quickly I found out I needed more travel.
So, now that brings me to my next dilema - bieng the hobbyist / fabricator that I am a simple 3 axis CNC is not "enough". I've dreamed up some 5 axis plans (nothing on CAD yet) and it actually seems easy enough to create...but I haven't seen a single build thread on a 5 axis DIY machine. I've searched for ever it seems and can't find anything. Maybe I have bad search terms or something..
So, here I ask.. I am looking for pics, links, videos to some good ol' DIY 5 axis setups..
post away cnczoners!
I'd like to see a CAD of what you have in mind.
Unless you are planning a 3+2 axis machine, I think CAM will be your biggest (or rather most expensive) problem. Getting zero-backlash on your rotary axes might also be tricky though.
There is a nice video of a DIY 5-axis running EMC2 here:
http://www.cnczone.com/forums/showthread.php?t=60243 (5 axis machining.)
My wife is a programmer, I'll get her to do it for me!
My "design" would be a lot like what you see in the video - except that the stepper for the rotary would be next to the rotary table with the stepper pulley pointing down. The rotary would have a timing pulley attached to the bottom, and of course the timing belt between the two. What kind of lash can you expect from that arrangement?
Otherwise I have 2 more choices.. one bieng to put the stepper on the bottom of the rotory table with direct drive - but there would be a height concern most likely. The 2nd option would be like what is posted in the first video - but on a larger scale. My concern with that design would be the weight of the head and the difficulty keeping it trammed.
Thoughts? Ideas? Suggestions?
If you drive the rotary table via the 'handle' then you will have the backlash between the table's worm wheel and worm gear to worry about as well.
If you direct drive it, you will lose the 90:1 gearing advantage that the worm gear gives you - I'd imagine a 200Nm stepper would be rather expensive if it even exists!
What do you plan to mill, and what sorts of cutting forces and speeds do you need?
It won't be a worked over rotary table if I can help it. That is the kind of info I need though, I am not really familiar with the abilities of the steppers in terms of Nm... and directly driving the rotary portion of the axis would not really be a "good" option because of the height it will take away from Z.
What kind of lash would be realistick from a timing pulley arrangement?
The goal is to use a bolt on 6" 3 jaw chuck. The stepper to rotate the chuck will sit right next to it with the shaft pointing down. A timing pulley on it, one on the bottom of the chuck and a belt in between. All of this will sit on a gantry of sorts that rotates in the opposite plane.
Not sure on the speeds and or forces, but, fwiw, it will be based around a Grizzly G0519 most likely. That should give you some idea.
edit - I don't expect to be cutting anything other than aluminum or 1018 with cutters .625 or smaller. most likely smaller.
Without trying to sound like a smart arse, I think you are going to have to do some Googling and calculations of your own here. Stepper torques are usually provided by the people who sell them, but you will need to do some maths to work out what sized steppers you will need before you start spending.
From what I have read, a stepper and a timing belt won't make a great 4-th axis - all commercial systems seem to use worm gears, harmoinic drives or multi-kW direct drive servos. The problem with using a stepper without a worm is that the cutting force can easily exceed the stepper's holding torque and drive the rotary axis backwards. Worm gears tend to be self-locking and are pretty much impossible to back-drive.
I would also suggest you work out the torque you are going to be putting on your 5th axis due to the weight of your 4-th axis and that 3-jaw chuck.
As for cutting forces - I wish I had a handy link for you - I can't seem to find the ones I used. IMHO though 0.625" is pretty large actually, and given that you said you want to cut aluminium with small cutters, shouldn't you be looking for something with way,way more rpm than that Grizzly (and coolant!)?
I guess I should have clarified a bit. In 5th axis usage, I doubt it will ever see over .375 dia. The only reason I mention the stepper/timing belt arrangement is that it seems to work on DIY (and even commercial) X and Y axis as far as accuracy is concerned.
What I trying to understand is why a 5th axis setup would have any different cutting forces on the steppers vs. the same steppers on the X or Y axis. The only major difference bieng that the power is bieng transferred through a ballscrew on X and Y - and with the rotary axes there will be no ballscrew, but a belt instead.. and one would be direct drive. I am going to search and see if I can find some pics of industrial type 5 axis components to see how thier abc axes work in relation to using a worm gear etc.. there has to be some sort of DIY way to do it.
the grizzly mentioned above, or I think I mentioned it above, would simply be a base to start with. In a DIY setup 4,000 RPM would be enough to run a .500endmill in a reasonable fashion I'd think. I'm not out to produce hundreds of parts..but more so to be able to say " I did it ". The work piece would be somewhere around 4x4x4.
The reason you don't see a lot more DIY 5-axis machines is simple: you have to spend more on software than on the mill to do anything useful.
Anybody who can hack together a CNC mill and use it will be able to build a 5-axis trunnion table-type setup. It's not hard and Mach and EMC2 can both run 5 axes. However, I think the cheapest CAM to run it is MasterCAM, and that's in the mid-thousands. 4-axis is considerably simpler though and you can get into the edges of it with free/low cost S/W and BobCAD has some support for it for real money but I think a good deal less than MasterCAM.
There is a use case for a 5-axis design to serve as basically a fancy fixture, e.g., to mill or drill on 5 faces of a cube. In this case the axes simply allow you to reposition the workpiece for conventional 3-axis milling without having to do a whole new setup using g-codes that can be calculated by hand or determined experimentally. Whether this is worth the trouble depends on your parts and how many of them you make. My suspicion is that it's not, for the vast majority of us, and thus why you don't see more 5-axis machines.
That's interesting looking software, but it doesn't look like a complete 5-axis solution to me. I'd really want to be able to simulate a 5-axis tool path before I let it run on a real machine - there are just so many more exciting ways to crash a 5-axis than a 3-axis!
I made a:
3D pointclaw scanner,
converter to solid,
dnc code generator.
All in Labview.
In 5 axis mode, not only the digitizer has to be better,
also the routing generator hast to be completely something else.
I don't see myself construction something like this, nor quickly use existing software who can.